Simulating new treatment for retinal degeneration

Human vision deals well with extreme contrasts of light levels in the environment – we can see in anything from weak starlight to glaring sunshine. The new study by Mutter and Münch shows the range of light intensity within which blindness can be treated using optogenetic methods. The process introduces light-sensitive proteins into the retina. Right: a cross-section of the retina, the different cell layers shown in different colors. Moon by John French, Abrams Planetarium. Image of retina by Hartwig Seitter © AG Münch, University Tübingen

For a few years now optogenetics has been seen as a very promising therapy for progressive blindness, for example when it is a result of retinal degeneration. In order to further develop this therapeutic approach, Marion Mutter and project leader Dr. Thomas Münch of the Werner Reichardt Centre for Integrative Neuroscience (CIN) and the Bernstein Center for Computational Neuroscience (BCCN) at the University of Tübingen have developed a computer model that simulates optogenetic vision. The research has been published in the November 27 issue of PLOS ONE.

Retinitis Pigmentosa is a form of in which the photoreceptors in the eye die off. In order to counteract the accompanying loss of light perception, light-sensitive proteins known as channelrhodopsins are introduced into the retina using an optogenetic procedure. Every cell that contains channelrhodopsins can be activated by exposure to light. After optogenetic treatment, neighboring cells can take over the lost functions of the photoreceptors. This procedure has already been successful in restoring in mice. Thus, in the last few years, the foundation has been laid for using optogenetics to treat blindness.

However, the method has its limits. Human vision normally deals well with extreme contrasts of light levels in the environment – we are able to see in anything from weak starlight to glaring sunshine. In contrast, 'optogenetic vision' with channelrhodopsins would only work in the very brightest sunlight – at least with the variants of channelrhodopsin that have been developed so far.

Improving the characteristics of channelrhodopsins is something to be hoped for, above all from the point of view of developing potential future applications in humans. The researchers developed and used a computer model to investigate how to achieve these improvements. This model makes it possible to assess how well different variants of channelrhodopsin would support restoring a sense of vision. "When one of these molecules is activated by light, it cycles through a defined set of states which ultimately determine the light response of the treated eye," explains Marion Mutter. Previously, improvements to channelrhodopsin were mainly pursued to carry out research into basic neurobiological questions. "Our results show that optogenetic vision would benefit from completely different improvements which have so far been overlooked," Marion Mutter and Thomas Münch say.

What effects would these improvements have on the sense of vision? "According to our calculations, it should be possible to see in brightness conditions that are one hundred times dimmer than what would currently be possible," explains Thomas Münch. According to his estimates, this would allow patients treated with optogenetic techniques to be able to see not only in sunlight, but also in a well-lit room. "At these brightness levels we reach the biophysical limits of what is possible with classic channelrhodopsin molecules," says Münch. "However, in our study we could also show why there are these limits, and so we provide a direction for novel types of improvements in the future."

More information: Marion Mutter & Thomas A. Münch (2013): Strategies for expanding the operational range of channelrhodopsin in optogenetic vision. PLOS ONE, DOI: 10.1371/journal.pone.0081278

Related Stories

A vision exam for mice

date Aug 21, 2013

How can one use simple means to investigate the visual abilities of animals? This question is being pursued by the research group of Dr. Thomas Münch at the Centre for Integrative Neuroscience at the University of Tübingen. ...

Light switches for nerve cells

date Apr 06, 2010

(PhysOrg.com) -- It sounds like a neurobiologist’s dream: a light-switch that allows nerve cells to be switched on and off at will. Three scientists have found just such a light switch and are now being ...

Altering eye cells may one day restore vision

date Jan 25, 2013

(Medical Xpress)—Doctors may one day treat some forms of blindness by altering the genetic program of the light-sensing cells of the eye, according to scientists at Washington University School of Medicine ...

Recommended for you

Closing the Australian eye health gap may be in sight

date 10 hours ago

Three years after the launch of the roadmap to close the gap for vision, progress has been made but "much remains to be done", according to the authors of a Perspective published online today by the Medical Jo ...

Pioneering gene therapy takes aim at inherited blindness

date Jun 29, 2015

Canada's first human gene therapy trial for eyes—the replacement of a faulty gene with a healthy one—is now underway at the Royal Alexandra Hospital to preserve and potentially restore vision for people ...

Iris research focuses on blood vessel patterns

date Jun 29, 2015

The structure of the microvasculature or blood vessels in the iris could play an important role in people's contraction of eye maladies like glaucoma and cataract, according to a WA-led study.

New nanotechnology drug to control blindness

date Jun 25, 2015

The Mexican company "Medical and Surgical Center for Retina" has created a way to deliver drugs in order to avoid risks and painful treatments in people with secondary blindness due to chronic degenerative ...

User comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.